This application relates generally to a scroll compressor, and more particularly to a scroll compressor including an eccentric pin having a drive surface with a contact area moved toward a distal end of the eccentric pin to improve stability of an orbiting scroll member.
Scroll compressors are becoming widely utilized in refrigerant compression applications. A scroll compressor typically includes a pair of scroll members that each have a base with a generally spiral wrap extending from the base. During operation, one of the two scroll members orbits relative to the other, which compresses a fluid entrapped between the wraps.
Scroll compressors utilize drive shafts to orbit the scroll member. The drive shaft has an end with an eccentric pin that is displaced from a rotational axis of the drive shaft. The eccentric pin is received within a bore of a slider block, which is further received within a boss in the orbiting scroll member. During rotation of the drive shaft, the eccentric pin engages the slider block, and in combination with an Oldham's coupling, moves the orbiting scroll member through an orbital path. A driving force is created at the point of contact between the eccentric pin and the slider block as the drive shaft rotates to move the orbiting scroll member through the orbital path. In addition, a gas force is created simultaneously with the driving force due to compression of the fluid entrapped between the spiral wraps. The driving force and the gas force face opposite directions and lie in separate planes.
Referring to FIGS. 1 and 1B, an eccentric pin 24 according to the prior art has a generally cylindrical outer surface 30 with a drive surface 38 formed along a length L of the outer surface 30. The drive surface 38 is generally flat with a slight crown 41 located near the middle of the drive surface 38 for providing single line contact with the slider block 26. Typically, the peak of the crown 41 is located on the drive surface 38 at a distance that is less than or equal to approximately 61% of the length L of the eccentric pin 24. The location of the peak of the crown 41 near the middle of the drive surface 38, in combination with the gas and driving forces being in separate planes, results in a large tipping moment of the orbiting scroll member. Disadvantageously, the large tipping moment may result in decreased stability of the orbiting scroll member and reduced compressor efficiency. Further, the tipping of the orbiting scroll member may cause diagonal wear on the drive surface, which moves the single line contact between the eccentric pin and the slider block to a lower position along the length of the drive surface. This increases the tipping moment even more, and may result in greater instability of the orbiting scroll member.
Accordingly, it is desirable to control the placement of the drive surface contact area of the eccentric pin to provide a scroll compressor with a more stable orbiting scroll member.